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Graham Rice on Trials

Updates on trials and awards from the Royal Horticultural Society by Graham Rice

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  • First season stars in the Wisley clematis trial

    Graham Rice on 25 Nov 2009 at 02:52 PM

    Clematis 'Jorma' - star of the Wisley clematis trial. Image: ©GardenPhotos.comNow that the assessment panel - which includes some of the country's leading experts in shrubs and climbers - has finished this year's sessions on the trial of Clematis viticella varieties, it's a good time to pick out those which they think have done best this year. I gave an early personal assessment, but the team has been checking the trial all summer right into the autumn.

    The star of the show so far has been ‘Jorma' (left, click to enlarge).  Its beautiful bluish-violet flowers were especially impressive and very uniform in colour with attactive stamens. However, the view was that this is not really a Viticella clematis but a Jackmanii type.

    Two old also favourites did well. ‘Alba Luxurians', white with green marks, was at its peak in mid August and still impressive a month later while the wine-red ‘Kermesina' also proved long flowering - its long season perhaps distinguishing it from the otherwise similar ‘Rubra'.

    Clematis 'Romantika' - a highlight of the Wisley clematis trial. Image: ©GardenPhotos.comSimilar to ‘Alba Luxurians' was ‘Luxuriant Blue' (entered as ‘Caerulea Luxurians') but with a blue tint to the white and green flowers indeed ‘Alba Luxurians' is one of its prents (the other is the rarely seen ‘Neodynamia').

    The deep purple blue ‘Blue Belle' proved better than the rather similar ‘Kiev' but became rather lanky later in the season while ‘Elvan', with pretty purple flowers striped in white, has nodding flowers so is best viewed from below. It was another with a very long season.

    ‘Hagelby Pink' was the best pink this year, and still had plenty of buds coming in mid September. It also flowererd all the way up the plant, a valuable feature. The panel agreed that it would look growing with the dark purple ‘Romantika' (above, click to enlarge), another Jackmanii type, which also stood out this year.

    In general the assessors noted that watering was a big help in extending the flowering period of these plants; on the trial this was provided soil level irrigation. But they decided that now that the plants are well established, next year they would not be watered unless absolutely necessary. This would provide a more realistic test.

    The plants will all be cut back to 15cm/6in in the spring - just as they would be in the garden. Next year's display promises to be even more colourful.

     
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  • Last days of the pampas grass trial

    Graham Rice on 18 Nov 2009 at 02:34 PM

    Cortaderia selloana 'Evita' - the star of the Wisley pampas grass trial. Image: ©GardenPhotos.comThe trial of Cortaderia, pampas grass, has been both dramatic and intriguing. As it comes to a close, with some entries still looking good very late in the year, there was one that stood out above all the others - ‘Evita' (click the picture to enlarge). Except part of the point is that it didn't "stand out" at all - some varieties are huge, 3m/10ft tall, but ‘Evita' is altogether more manageable.

    Reaching just 4-5ft/1.2-1.5m high, it combines vigour, dwarf habit, prolific flowering with plumes of good substance and also flowers as a young plant - a very valuable feature. Another notable feature is that ‘Evita' plants are female, but are not known to produce seed. I'm certain this will get an Award of Garden Merit.

    One of the interesting things about cortaderias is that plants are either male or female so any seedlings produced will be hybrids. So when nurseries raise named varieties from seed the resulting plants will not come true - and there was some dramatic evidence of this in the trial; no awards for those entries.

    But others that looked especially good included. ‘Highfield Pink' which was seen as the best pink-flowered form - and one assessor said it had an "Afghan Hound quality"! The variegated ‘Pink Phantom' also impressed.

    Cortaderia selloana Silver Feather 'Notcort' - the best for foliage in the Wisley pampas grass trial. Image: ©GardenPhotos.comThose with variegated foliage must obviously be propagated by division and two of these stood out. Silver Feather (‘Notcort') is a white variegated form of C. pumila and the overall impression of the rather discreetly marked leaves was of grey foliage. It flowered well, did not grow too high (in fact it was one of the smallest) and its foliage was excellent.

    The other good variegated plant was ‘Gold Band'. More vigorous than other variegated types, the overall effect was a wonderful golden colouring and the flowers were excellent too.

    These were the stars of the trial and as well as identifying some excellent plants small enough for most gardens and which will give colour from both flowers and foliage, it really highlighted the necessity for nurseries to propagate by division and not seed.

    I'll bring you news of the final awards once they're confirmed. In the meantime, take a look at the full list of plants in the Cortaderia trial.

     
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  • Two fine late flowering kniphofias

    Graham Rice on 11 Nov 2009 at 12:31 PM

    Kniphofia rooperi - a fine very late flowering poker. Image: ©GardenPhotos.comA week or two back I wrote about delphiniums which came back for a second burst of flowers long after their main flush in June. The last couple of times I was taking a look at the Wisley flower trials I also noticed some other perennials looking good late in the season.

    The Kniphofia trial has been a difficult one to assess because these pokers flower over such a very long season - some are at their peak in late spring, some in mid autumn.

    In September and October Kniphofia rooperi (above, click to enlarge) has been spectacular. You can see from the picture how vivid it is and how few other kniphofias there are flowering in the background.  This is a splendid plant for autumn colour and because this form in the trials, sent to the trial by the Hampshire nursery MacGregor's Plants for Shade, was so good it was decided that it needed its own cultivar name. As yet, we don't know what that will be. But this plant was certainly better than the variety ‘Torchlight' growing alongside.

    Kniphofia caulescens (from John May) - good foliage and good flowers. Image: ©GardenPhotos.comThe other poker at its peak late in the season was K. caulescens, and in particular the form loosely known as "from John May". This is very different from many pokers in that not only are its spikes at their best in the autumn, but its impressive foliage is a valuable feature for many months.

    Its leaves are relatively broad and noticeably greyish in colour, sometimes they look rather like the leaves of leeks, and can be very dramatic. You can see them in the background in the picture. And it turns out that his plant is unusual in another way: in South Africa, where it grows wild, it's seen in large colonies in bogs - far wetter conditions than we normally associate with kniphofias.

    Both these late flowering pokers look to be well on their way to gaining the Award of Garden Merit and will bring a little fiery style late in the season.

     
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  • Awards for irises

    Graham Rice on 06 Nov 2009 at 12:09 PM

    Iris 'Helen Dawn' - Award of Garden Merit winner 2009. Image: ©RHSTall Bearded Irises are amongst the most dramatic and colourful of perennials so the very best of them must be really impressive. And they are.

    The RHS Iris Sub Committee - yes, there's a sub committee just for irises - has recently had its latest awards ratified and three Tall Bearded Irises performed so well in the trial at Wisley that they've been given the Award of Garden Merit.

    They were planted in 2007 on the Portsmouth Field, usually known just as the trials field, and were assessed regularly during the flowering season. Using a points system, four specific qualities assessed: the overall quality of the plant, stem quality (robustness and branching), flower quality and the presentation of the flowers.

    And out of 110 entries into the trial three gained an AGM, while one other had its AGM withheld until it becomes available to buy.

    The lovely ‘Helen Dawn' (above, click to enlarge) is almost pure white. Reaching about 90cm/3ft, with six to eight buds on each stem, the standards (the three upper petals) are almost pure white while the falls (the three lower petals) are slightly creamier with an attractive network of pale veins. The white beard is yellow at the tip, deepening almost to orange in the throat, and the flowers have what iris-expert Claire Austin calls a "heavy sharp scent".

    ‘Helen Dawn' was raised by Australian breeder Graeme Grosvenor and registered back in 1998. It's a cross between ‘Skating Party' and ‘Scandia Delight'.

    Iris 'Diabolique' - Award of Garden Merit winner 2009. Image: ©RHS‘Diabolique' is almost the opposite in colour. The nearly-black buds open to heavily ruffled deep wine purple flowers, the falls slightly richer and more vinous than the standards. The blooms have good substance so are unusually weather resistant while the deep blue beard is short, but its colour stands out well. Reaching about 38in/97cm and with up to nine flowers on each stem, ‘Diabolique' makes quite an impact.

    Raised by the prolific Schreiner's Gardens in Oregon, ‘Diabolique' has ‘Amethyst Flame' and ‘Melodrama', amongst others, in its background.

    Also from Oregon is the last of the three Tall Bearded Irises to be given an AGM for 2009, ‘Paul Black'. This is taller, at 4ft/1.2m, with up to six buds per stem and is basically dark purple-blue with a fiery orange beard - like a flame in the night. Both the standards and the falls have a slightly inky look but fade to white in the throat. ‘Paul Black' was raised by Thomas Johnson and named for his partner at their iris nursery Mid-America Garden in Oregon

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